CN2760762Y - Gallium nitride-based light-emitting diode structure - Google Patents

Abstract

The utility model relates to a gallium nitride light-emitting diode structure, which comprises a substrate; a semiconductor stack layer connected to the upper part of the substrate and including an n-type GaN layer, a light emitting layer, and a p-type GaN layer from bottom to top; a roughened layer above the p-type GaN layer; a conductive transparent oxide layer located above the roughened layer and forming ohmic contact with the roughened layer; a first electrode electrically coupled to the n-type GaN layer in the semiconductor stack layer; and a second electrode electrically coupled to the conductive transparent oxide layer. The light-transmitting conductive oxide layer is formed on a gallium nitride contact layer with a surface roughened layer and serves as a window layer, the roughened layer serves as an ohmic contact layer with the light-transmitting conductive oxide layer, contact impedance and working voltage can be effectively reduced, the roughened layer interrupts a light guide effect, light extraction efficiency is improved, and external quantum efficiency is further improved.

Description

Gallium nitride-based light-emitting diode structure

technical field

The utility model relates to a gallium nitride light emitting diode structure, in particular to a gallium nitride light emitting diode structure with a better ohmic contact layer.

Background technique

The traditional structure of a gallium nitride-based light-emitting diode device is shown in Figure 1. The traditional light-emitting diode structure 10 includes a substrate 11, a gallium nitride buffer layer 12, an n-type gallium nitride layer 13, an indium gallium nitride Light emitting layer 14, a p-type gallium nitride layer 15, a p-type gallium nitride contact layer 16 (layers 12 to 16 are referred to as epitaxial structures) and a transparent conductive layer (transparent conductive layer) 17; in addition, A p-type metal electrode 18 is located on the transparent conductive layer 17 , and an n-type metal electrode 19 is located on the n-type GaN layer 13 .

According to known technologies, the conductivity of the p-type GaN ohmic contact layer 16 is rather low, and the current is easily confined under the P-type metal electrode 18 . Therefore, in order to effectively disperse the current to achieve uniform light emission, a transparent conductive layer 17 must be formed on the p-type gallium nitride ohmic contact layer 16 and cover the entire light emitting area, and in order to improve the light transmittance, this The transparent conductive layer 17 must be relatively thin. Wherein, the traditionally used transparent conductive layer may be composed of nickel/gold, but in order to increase light extraction (light extraction) efficiency, a roughened structure may be formed on the surface of the LED. At this time, if thin nickel/gold is used as the transparent conductive layer, the effect of lateral current spreading is not uniform, and the phenomenon of partial luminescence is particularly prone to occur, which will lead to an increase in operating voltage (the nickel/gold transparent conductive layer shown in Figure 4A and Figure 4B Combination of photoconductive layer with rough surface and I-V curve).

The well-known Indium Tin Oxide (Indium Tin Oxide) is called ITO for short. It is not only a high energy gap material with an energy bandgap between 2.9 and 3.8 electron volts, but also has a transmittance of over 95% in the visible light range. It is an n-type high-conductivity material with high conductivity. The refractive index of this indium tin oxide (ITO) is between 1.7 and 2.2. According to Snell's law and anti-reflection principles, due to the multilayer nitrogen The distribution of the refractive index (n=2.4) of the GaN epitaxial structure and the refractive index (n=1.5) of the resin capping material used for packaging, if an intermediate medium with a refractive index n ~ 1.9 can be added, it can be reduced after packaging. The reflection of light further increases the efficiency of light extraction, so this material is very suitable for use as a window layer of light-emitting diodes.

In recent years, although the technology of using indium tin oxide (ITO) as a transparent conductive layer has been proposed, such as the indium gallium nitride light-emitting diode described in Taiwan Patent Publication No. 461126, as shown in FIG. 2 , the diode structure 20 has a Substrate 21, a gallium nitride buffer layer 22, an n-type gallium nitride layer 23, an indium gallium nitride active layer 24, a p-type gallium nitride layer 25, a p-type contact layer 26, a transparent conductive Oxide layer 27, a p-type electrode 28 and an n-type electrode 29; wherein, although the transparent conductive oxide layer 27 is indium tin oxide suitable for light emission, in this diode structure, the surface of the p-type contact layer below it is It is relatively flat Ga-polarization (Ga-polarization) surface, it is difficult to form a good ohmic contact with ITO, so the contact resistance between the two is high and the ohmic contact characteristics are not good, so the operating voltage of the light-emitting diode is difficult to drop .

In view of the aforementioned disadvantages of poor ohmic contact characteristics and high operating voltage, it is necessary to propose a structure for improving the ohmic contact characteristics between the indium tin oxide layer and the p-type gallium nitride layer.

Contents of the invention

The utility model is a gallium nitride light-emitting diode structure with a better ohmic contact layer, wherein the main purpose is to form a light-transmitting conductive oxide layer on a gallium nitride contact layer with a textured layer , and use the roughened layer as an ohmic contact layer with the light-transmitting conductive oxide layer, the light-emitting diode structure includes: a substrate; a semiconductor stack layer connected to the top of the substrate, including from bottom to top An n-type GaN-based layer, a light-emitting layer, and a p-type GaN-based layer; a roughened layer located above the p-type GaN-based layer; a conductive light-transmitting layer located above the roughened layer oxide layer, and form an ohmic contact with the roughened layer; a first electrode, electrically coupled with the n-type gallium nitride layer in the semiconductor stack layer; and a second electrode, electrically coupled with the conductive light-transmitting oxide layer sexual coupling.

According to the idea above, the roughened layer can be an n-type, p-type doped or double-doped GaN-based layer.

According to the above idea, the light-transmitting conductive oxide layer can be indium oxide, tin oxide or indium tin oxide.

According to the above idea, the light-emitting layer is a GaN-based layer composed of indium.

According to the above idea, the roughened layer is a nitrogen polarized surface layer.

Thereby, the contact resistance and working voltage can be effectively reduced, and at the same time, the roughened layer interrupts the photoconductive effect, increases the light extraction efficiency, and further improves the external quantum efficiency.

Description of drawings

Figure 1 is a schematic diagram of the structure of gallium nitride-based light-emitting diodes in common technology;

Figure 2 is a schematic diagram of the structure of an indium gallium nitride light-emitting diode in common technology;

Fig. 3 is a structural schematic diagram of a gallium nitride-based light-emitting diode of the present invention;

Figure 4A shows a partial luminescence diagram produced by the combination of a nickel/gold light-transmitting conductive layer and a rough surface in a common technique;

Figure 4B shows the I-V curve diagram of the combination of nickel/gold light-transmitting conductive layer and rough surface in common technology;

Fig. 5A shows the combination of indium tin oxide light-transmitting conductive layer and rough surface without partial luminescence in the present invention;

FIG. 5B shows the I-V curve of the combination of the ITO light-transmitting conductive layer and the rough surface in the present invention.

Wherein, the reference signs are explained as follows:

10 Light-emitting diode structure 11 Substrate

12 GaN buffer layer 13 n-type GaN layer

14 Indium nitride light-emitting layer 15 p-type gallium nitride layer

16 p-type gallium nitride contact layer 17 transparent conductive layer

18 p-type metal electrode 19 n-type metal electrode

20 Diode Structure 21 Substrate

22 GaN buffer layer 23 n-type nitride graft layer

24 InGaN active layer 25 p-type GaN layer

26 p-type contact layer 27 transparent conductive oxide layer

28 p-type electrode 29 n-type electrode

30 Light Emitting Diode 31 Substrate

31’ Buffer layer 32 n-type gallium nitride layer

33 luminescent layer 34 p-type gallium nitride layer

35 p-type contact layer 36 roughened layer

37 Window layer 38 1st electrode

39 second electrode

Detailed ways

Please refer to FIG. 3 , which is a preferred embodiment of the GaN-based LED structure of the present invention. As shown in the figure, the GaN-based light-emitting diode 30 of the present invention has a structure of a substrate 31, an n-type GaN-based layer 32, a light-emitting layer 33, a p-type GaN-based layer 34, and a p-type GaN-based layer 34. Type contact layer 35, a textured layer 36, a window layer 37, a first electrode 38 and a second electrode 39, wherein a buffer layer 31' may also be included above the substrate 31.

The structure disclosed in the present invention is a semiconductor stack layer connected above the substrate 31, including an n-type gallium nitride-based layer 32, a light-emitting layer 33, a p-type gallium nitride-based layer 34, etc. from bottom to top. In addition, the The roughened layer 36 is located above the p-type GaN-based layer 34 and the p-type contact layer 35 . The window layer (window layer) 37 is a conductive light-transmitting oxide layer located above the roughened layer 36, forming an ohmic contact with the roughened layer. The first electrode 38 is provided, which is electrically coupled with the n-type GaN-based layer in the semiconductor stack layer, and the second electrode 39 is electrically coupled with the conductive light-transmitting oxide layer.

The substrate 31 can be a sapphire, gallium oxide, lithium gallium oxide, lithium aluminum oxide, spinel, silicon carbide, gallium arsenide or silicon substrate. The n-type GaN-based layer 32 is an n-type doped GaN, AlInGaN or InGaN layer. The p-type GaN-based layer 34 is a p-type doped GaN, AlInGaN or InGaN layer. The light emitting layer 33 is a nitride compound semiconductor containing indium. The window layer 37 is a conductive light-transmitting oxide layer, which can be indium oxide, tin oxide or indium tin oxide.

The presence of the textured layer (textured layer) 36 disposed between the p-type contact layer 35 and the window layer 37 can not only increase the light extraction (light extracting) efficiency, but also cause a large amount of light output due to the rough surface and interrupt the light guiding effect. , its surface state (surface state) can be deliberately controlled into a nitrogen polarized surface during the epitaxial growth process, which has been described in Taiwan Patent Application No. 92136888, thereby reducing the window layer 37 and the second conductivity type GaN-based layer The contact resistance between 34 becomes an excellent ohmic contact layer and reduces the operating voltage of the diode (as shown in FIG. 5A and FIG. 5B the combination and I-V curve of the ITO light-transmitting conductive layer and the textured surface).

Compared with the known technology shown in FIG. 4A , because of the inhomogeneous current lateral distribution effect, the combination of the nickel/gold light-transmitting conductive layer and the woven surface produces a partial luminescence 40 phenomenon in which the current distribution around the second electrode is uneven, the utility model As shown in FIG. 5A , when the light-transmitting conductive oxide layer is used instead of the nickel/gold light-transmitting conductive layer and combined with the textured surface, there is no localized luminescence around the second electrode. In addition, the roughened layer 36 can also be an n-type, p-type doped or double-doped GaN-based layer.

The above-described embodiments are only preferred embodiments of the present utility model, and those skilled in the art can derive various embodiments after reading the description of the above-mentioned embodiments, but these embodiments all belong to the present utility model In the range.

Claims (5)

1. LED structure with gallium nitride system is characterized in that comprising:

One substrate;

The semiconductor stack layer is connected to the top of this substrate, from bottom to top comprises a n type gallium nitride series layer, a luminescent layer, a p type gallium nitride series layer;

One roughening layer is positioned at the top of this p type gallium nitride series layer;

One conduction printing opacity oxide layer is positioned at this roughening layer top, and forms ohmic contact with this roughening layer;

One first electrode is with the n type gallium nitride series layer electrical couplings in this semiconductor stack layer; And

One second electrode is with this conduction printing opacity oxide layer electrical couplings.

2. GaN series LED as claimed in claim 1 is characterized in that this roughening layer can be the n type, the p type mixes or the gallium nitride series layer of codope type.

3. GaN series LED as claimed in claim 1 is characterized in that this light transmitting conductive oxide layer can be an indium oxide, tin oxide or tin indium oxide.

4. GaN series LED as claimed in claim 1 is characterized in that this luminescent layer is one to contain the gallium nitride series layer of indium.

5. as claim 1 a described GaN series LED, it is characterized in that this roughening layer is a nitrogen polarized meter surface layer.

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